Boiler efficiency meter



, 8, 1929. J. M. SPITZGLASS 1,730,54f

BOILER EFFICIENCY METER Filed May 1. 1926 &

Patented Oct. 8, 1929 UNITED STATES PATENT OFFICE JACOB M. SPITZGLASS,OF CHICAGO, ILLINOIS, ASSIGNOR TO REPUBLIC" FLOW METERS COMPANY, OFCHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS BOILER EFFICIENCY METERApplicaticn filed. May 1, 1926. Serial No. 105,957.

My invention relates to methods for controlling apparatus for generatingor using power, and one object of the invention is to provide means bywhich the operator may at all times be apprised of the conditionsexisting in the apparatus so that if he observes that any of them are atvariance with those which have been predetermined as being mostadvantageous, they may be corrected,

thus causing the apparatus always to function with maximum efficiencyeven though the capacities at which it is operating change from time totime. For illustration, take the case of a steam generating plant inwhich fuel is employed to generate the heat. Ordinarily the demands uponthe boiler will vary from time to time. My apparatus is designed to makeit possible for the operator in charge of the boiler room to so controlthe conditions of operation as to produce maximum efficiency at thevarious capacities at which the boiler is called upon to operate. Thesteam flow, that is, the rate at which the boiler must produce steam,depends, in the case of a factory, upon the amount of power required, orin the case of a heating plant, on

' the amount of heat which must be supplied.

This factor of steam flow, therefore, while variable, is not,practically speaking, under the control of the man in charge of theboiler room but is dependent upon exigencies beyond his control, such aspower or heat requirements. Consequently the steam flow or boilercapacity is the given or predetermined factor, and one purpose of theinvention is to provide a method and means for keeping the operatoradvised as to the capacity at. which the boiler is operating and alsokeep him advised as to other correlative conditions or factors so thathe may be able to modify them in such manner as to obtain maximumefficiency. Another object of the invention is to provide means by whichthe operator may readily compute the efficiency at which the boiler isoperating at any given moment. Another object is to. provide means bywhich a permanent record of the various conditions or factors may bemade and the efliciencies computed.

Boiler efiiciency is obtained in practice by determining the loss ofheat due to improper combustion of fuel in the furnace and improperabsorption of heat in the boiler.

In ordinary boiler room operation most of the loss is the heat carriedaway through the stack by the heated gases. Improper combustion (causedby feeding too much air) increases the weight of gas per pound of fuelso that more pounds are heated from room,

to stack temperature for each pound of fuel. Besides, such impropercombustion causes a reduction in the furnace temperatures, which initself reduces'the possible transfer of heat to the boiler. Improperabsorption or transfer of heat to the boiler, increases the temperatureof the escaping gases. The product of the two forms the so-called stacklosses, which have been found in all cases to be indicative of the totalloss of heat through the boiler.

Let L signify the percent loss in the boiler, and W and T the weight andtemperature of. the escaping gases respectively. Then L=KWT 1 consideredis the difference between the room temperature and the temperature oftheflue gases at the .last pass in the boiler or at the base of the stack,buta scale may be readily prepared to read direct in degrees above theroom temperature and T will therefore be understood as representing thedifference in temperature or the rise-above room temperature.

The value of 7 cannot be obtained directly, but it has been found byexperience based on. numerous tests and experiments that the per cent ofcarbon dioxide in the flue gases is a direct index of the amount of airused for the combustionof the fuel (it being understood, of course, thatin the practical operation of a steam boiler a greater amount of airthan that theoretically required for complete combustion is alwayssupplied, such excess resulting in the proportionate reduction of the COcontents in the flue gases). Consequently the amount of CO in the gasesis an index of the weight of the gases passing through the stack perpound of fuel. Hence we may write W=a function of P. (2)

That is, the Weight of gases'per pound of fuel is a function of P whereP represents the percent of CO in the products of comwhere C is aconstant. This substitution is close enough for practical purposesalthough in the actual construction of my apparatus the scale may bemade according to the 1noreaccurately determ ned relation of W to P.

Combining Equations (1) and (2) we have and by calling K=CK, we have Toillustrate the application of this equation; let it be assumed that agiven fuel, say western bituminous screenings, having a 0 heat value of11,000 E. t. u. per pound, re-

quires a minimum weight of 8.4: pounds of air for perfect combustionresulting in a maximum of 18.4 per cent of CO In practice, it is firstnecessary to obtain othe characteristics of the particular .boilerforwhich the instrument is to be used and for this purpose severaltestsare run on the performance of the boiler. Let it be assumed that a testshows that when T is equal to 500 (sodegrees F., and P is equal to 10per cent 6 With a knowledge of these conditions, we

solve for the value of K from Equation For convenience we let Trepresent units of temperature, 100 degrees F each. Then Thus the lossmay be computed at any time by observing the temperature and the percentof CO and this formula will hold substantially true for variouscapacities or rates of steam flow ofthe particular installation underobservation.

To give a concrete illustration of the method and operation of theapparatus, reference may be had to the accompanying diagram in which arecord strip a is causedto travel beneath styluses b, 0, and (Z. In thepresent case, the strip is assumed to travel downward and as mechanismfor causing record strips to travel are Well known such mechanism neednot be described here. The sheet has cross rulings e which indicate thevarious hours of the day, these hours being denoted by appropriatemarkings 7 here shown in a column at the left margin of the strips Thestrip .is divided into three sections arrangedside by side, the section9 at the left representing steam flow, the section I), at the middlerepresenting the percent of ()O and the section at the right represent.ing the stack temperature, or more properly speaking, the differencebetween the ,stack ten'iperature and the temperature of the boiler room.

The steam flow section 9 has vertical rulings or ordinates is spacedequally and TBPIQ. senting units of steam flow. These units areindicated by a row of numerals m which in the present illustrationprogress from left to right in increments of ten. These units areselected arbitrarily and the operator may, if he wishes, translate theseunits intoactual pounds of steam generated per hour.

The CO section It has vertical rulings or ordinates a spaced equally andrepresenting the percentage of CO These percentages are indicated by arow of numerals j) which in the present illustration progress from leftto right in increments of two.

The stack temperature section at the right has vertical rulings 7 thatare spaced equally and represent stack temperatures. These temperaturesare indicated by a row of numerals s which progress from lift to rightin increments of one hundred.

Said rows m, p and s of numerals may be printed directly upon the recordstrip at intervals or they may be markedon a stationary portion of theapparatus in suchposi'tionthat stacktemperature.

the vertical lines or ordinates k, n, 1' will pass under them inuxtaposition thereto.

The styluses b, 0, (Z, may be supported and operated by any appropriatetype of mechanism so long as they are moved in accordance with thevariation of the factors which they represent. In the present case,which is largely diagrammatic, the styluses are supported upon rods tslidable upon a guide bar a and controlled by rods w, 11 a which aremoved by suitable devices in accordance with the variable factors ofsteam flow, percentage of CO and stack temperature. For example, the rod02 may be operated by a steam flow meter, which is a known instrument,and the rod 3 may be operated by a gas analyzer which will indicate thepercentage of (30,, such instruments also being known. The rod :4 may beoperated by a pyrometerwhich is also a known instrument.

The styluses b, 0, and d trace graphs B, C, D respectively on the recordstrip and from the considerations above stated it will be evident thatthe loss will be least and the efficiency greatest in proportion as thegraph G moves towaird the right and the graph D moves toward the left.Thus by merely noting the by noting the distance between the two graphs.

But my device in its developed form goes further than this and is soconstructed that the observer may by making a simple multiplication oftwo numerals calculate the efliciency at which the boiler is operating.The mechanism more intimately concerned with this characteristic willnow be described.

The bridge 1) is mounted in front of the record strip and heldstationary by screws Q) or other suitable fastening means. In the formillustrated, it consists of glass, celluloid or other transparentmaterial, although this is not essential. On this bridge isjuxtaposition to scale 8 there is marked a scale s in which the numeralsrepresent units of temperature. The integers in the present illustrationrun from 0 to 9, progress from left to right, and each unit represents100 degrees of This scale represents the temperature factor T ofEquation No. (3) and it will be noted that it progresses in the samedirection as the scale s, and that the zero point is at the line R.

On said bridge 1: in juxtaposition to scale p there is marked a scale pin which the numerals progress in the opposite direction from scale 39.These numerals are marked to represent the values of in Equation No.

represents the WVfactor, although as this is determined according to mymethod from the CO factor in the flue gases, in the parlance of theboiler room the scale p is more aptto be referred to as the CO factorand is so marked in the diagram. In the form illustrated scale p runsfrom i to 18 with the graduations gradually decreasing in extent. towardthe higher portion of the scale.

The scales 7), s as stated are calibrated according to Equation No. (.3)so that by multiplying the readings on thesetwo scales together theproduct will give'the percent loss in the efficiency of the boiler.v Theresult is that my instrument provides means by which the heat losses maybe obtained by simply multiplying together the readings on the twoscales s, and the efficiency may readily be obtained by subtracting thisloss from unity or 100%.

From the foregoing it will be evident that the device illustratedconstitutes a boiler efficiency meter and embodies in a singleinstrument means for indicating or recording three variable factors, vizsteam flow, stack temperature and percentage of the carbon dioxide inthe stack gases, the later factor in my device being interpretable interms of the weight of flue gases per pound of fuel. Thus the operatormay be appraised at all times of the actual conditions of operation, andhe is afforded simple and reliable means by which he may, by an easycomputation, calculate the efficiency at which the boiler is operating.

According to the arrangement illustrated, the graphs C and D approacheach other as the efficiency increases and recede from each other as itdecreases, but it will be understood, of course, that this arrangementmay be reversed without departing from the spirit of the invention, forby reversing the scales p, s and reversing the movement of theindicators 0, d the efliciency will be greatest when the graphs 0, D arefarthest apart and, least when they are closest together. The presentarrangement, however, is preferred, for according to it the zero pointsmay be located on a common line (in the present case line B) and theinstrument will present a more graphic and readily understood picture tothe mind of the operator.

Having thus described my invention what I claim as new and desire tosecure by Let ters Patent is:

1. The method of determining a factor ap proximately proportional to theloss of efliciency in a furnace, which consists in measuring thepercentage of carbon dioxide in the flue gases and their temperature onreaching the stack, determining the temperature of the air in thefurnace room and multiplying the difference between these temperaturesby the reciprocal of the said carbon dioxide percentage. a

2. The method of determining a factor approximately proportional to theloss'of eificiency in a furnace, comprising obtaining an index of thestate of the flue gases by measur ing the percentage of carbon dioxidetherein, and determining the temperature of the flue gases in the stack,determining the temperature of the air supplied to the furnace, andmultiplying the difierence between these temperatures by the reciprocalof the said carbon dioxide percentage.

In Witness whereof, I have hereunto subscribed my name. 7

JACOB M. SPITZGLASS.

